287 invites went out. 350 people showed up. And he expected them to all stay quiet.

Sacks runs what's been called the "Facebook for business"—but guests weren't supposed to use social media or photo-sharing services at all at the party, which also marked his upcoming fifth wedding anniversary.

The theme: "Let him eat cake." Costume shops from San Francisco to Los Angeles ran out of 18th-century French dresses and suits. Some guests had gowns custom-sewn for the occasion.

Despite this, they weren't supposed to discuss even the existence of the party, as Sarah Lacy, editor of the PandoDaily tech news site, discovered to her dismay.

Guests were uncomfortable with the publicity, Sacks told her in an email that Lacy received as she was in the security line at the airport heading to the party.

One guest said the party cost $1.4 million. We have no idea where he got that figure, but we can see why someone would guess a number in that ballpark. It was held at the $125 million Fleur de Lys mansion in Beverly Glen—one of the 10 most expensive homes in America. And Snoop Dogg was the entertainment.

If it really cost that much, it's about one-tenth of one percent of what Microsoft is reportedly going to pay for Sacks's company.

Luckily for you, some of the invitees broke the rules and let slip some glimpses of the party.

UPDATE: We originally reported that a thousand people had been invited. A source close to the matter subsequently provided us with the actual numbers. We also identified Nikhil "Ra" Sharma as an owner of Division Entertainment, as he states on his LinkedIn profile, but the company tells us that he is not an owner.